Research On Error Comrensation Algorithm Based On Single-pole Magnetic Encoder

In recent years,the wave of miniaturization and integration of industrial equipment has emerged.Small control equipment,especially hand-held head and unmanned aerial camera,has developed rapidly.Common position sensors include optical encoders,rotary transformers and multipole magnetic encoders.However,various small control devices have strict requirements on their own volume and weight.Traditional position sensors are difficult to be lightweight and miniaturized due to their complex detection structure,so they are difficult to be applied in these devices.single-pole magnetic encoders are widely used in small aerial photography and portable head control equipment due to their small size,low cost and easy integration.However,the output accuracy of the single-pole magnetic encoder is very sensitive to the mechanical error caused by the encoder installation process,which results in the single-pole magnetic encoder's accuracy is generally lower than the traditional position sensor.Therefore,the design of a decoding algorithm that can compensate the input signal deviation caused by mechanical error is of great significance to the development of single-pole magnetic encoder.Firstly,in order to improve the quality of input signal,a signal preprocessing algorithm based on modified clipping filter and quadratic exponential smoothing is proposed.In addition to effectively removing salt and pepper noise and increasing the smoothness of the signal,the algorithm has the advantages of low delay and low computation.In order to solve the disadvantages of single-pole magnetic encoder,such as low output accuracy and sensitivity to installation deviation,the magnetic field distribution and signal generation process in single-pole magnetic encoder are simulated and analyzed theoretically in detail.On this basis,four ways of deviation of input signal from ideal state caused by installation deviation of single-pole magnetic encoder are studied in this paper.DC bias,the phase is not orthogonal,the high-order harmonic noise in the signal is analyzed deeply,the mathematical expression of each kind of error is deduced,and the variation curve of error in different angle positions is drawn through MATLAB simulation.According to the error and the relationship between the deviation of the input signal,this paper puts forward two methods of error correction,one is based on discrete Fourier transform of the input signal amplitude and phase are analyzed to solve the formula method,the second is to use the output error in different angular position of the circumference of the existence of extremal phenomenon,by adding a set of 45 phase spacing hall peak phase change law of the input signal to avoid the error.In order to test the accuracy of the algorithm,hall sensor is selected as the magnetic induction element,delta servo motor with 16-bit output accuracy is taken as the reference,and the algorithm accuracy verification platform is built according to the structure principle of the monopole magnetic encoder.The difference of output precision between the traditional decoding algorithm,the arctangent and calibration table lookup method and the algorithm with error correction under different installation deviations is compared.On this basis,the performance of AMS AS5045 single-pole magnetic encoder and decoder chip is compared.The experimental results show that the algorithm with error correction has strong robustness to installation deviation.Compared with the traditional decoding algorithm,the improved algorithm can improve the accuracy by 6～7 times to 0.2°,which is better than the AS5045 single-pole magnetic encoder decoding chip.